1. Field of the Invention
The present invention relates to a control device of an internal combustion engine.
2. Description of the Related Art
Known in the art is a control device of an internal combustion engine setting an intake air amount in accordance with an amount of depression of an accelerator etc. expressing a requirement of the driver of the vehicle (that is, the target intake air amount), finding a target opening degree of the throttle valve based on the required intake air amount (that is, the target throttle opening degree), and controlling the opening degree of the throttle valve (that is, the throttle opening degree) to this target throttle opening degree to control the intake air amount (for example, see Japanese Unexamined Patent Publication No. 5-65845).
In such a control device of an internal combustion engine, the target throttle opening degree is made a throttle opening degree whereby the pressure in the intake pipe at the downstream side of the throttle valve becomes the intake pipe internal pressure for realizing the required intake air amount (that is, the required intake pipe internal pressure). Further, on the other hand, in general, the effect of a change of the opening degree of the throttle valve on the intake pipe internal pressure (that is, the effect on the intake air amount) becomes extremely small in the region with a large throttle opening degree, that is, in the region with a large intake pipe internal pressure.
From this, in the region with a large throttle opening degree, that is, in the region with a large intake pipe internal pressure, even if the operating conditions of the engine change slightly and the required intake air amount changes slightly correspondingly, the throttle opening degree is made to greatly change to realize a change of the required intake pipe internal pressure corresponding to this and hunting of the throttle opening degree occurs in some cases. Further, the occurrence of such hunting has a detrimental effect on the durability of the throttle valve and also becomes a factor causing deterioration of the robustness of control.